Current growth rates for the digital magnetic recording data storage industry show a significant annual increase in recording densities and transfer rate and a decrease in seek time. To continue on this growth rate curve, the recording industry is being forced to make a number of significant changes in the design and operation of the magnetic recording device. Digital magnetic recording devices for data storage generally comprise a thin film magnetic recording disk, a spindle motor for rotating the disk, and a head or transducer which is moved along or above the surface of the rotating disk to read and write information on the disk. The thin film magnetic recording disks generally comprise a substrate, a magnetic layer such as a cobalt-based metal alloy, a protective amorphous carbon layer and a layer of perfluoropolyether disposed on the carbon overcoat. The magnetic recording disks are mounted on a spindle motor which rotates the disk at a high rotational speed. The spindle motor generally comprises (i) a spindle shaft attached to a housing (ii) a spindle hub rotatably mounted on the shaft and (iii) lubricant covered ball bearings positioned in races formed in the shaft and/or hub.
The head or transducer is attached to a carrier or slider having an air bearing surface which is supported during operation adjacent the data surface of the disk by a cushion of air generated by the rotating disk.
The recording device also comprises a positioning actuator connected to the carrier for moving the head to the desired location on the disk during reading or writing operations.
Conventional magnetic recording devices are operated at a rotational speed of about 3600 RPM to 7000 RPM. It has been discovered that during normal operation of the disk drive at higher rotational speeds e.g., greater than 7500 RPM, the recording device begins to undergo acoustic vibrations associated with chemical breakdown of the spindle bearing grease lubricant within a short period of time. Continued operation of the recording device in the presence of the acoustic vibrations leads to mechanical failure of the spindle bearing.
It is an object of the present invention to provide an improved magnetic recording device which operates for extended periods of time at higher rotational speeds without unacceptable acoustic vibrations.
Other objects and advantages will be apparent from the following disclosure.